This invention relates to methods of inhibiting or killing tumor and cancer cells in human patients using aryl N-substituted carboxamides such as N-substituted benzamides and nicotinamides as direct chemotherapeutic agents or as sensitizers for radiation and/or other chemotherapeutic agents, and to novel aryl N-substituted benzamides and nicotinamides for such use.
A variety of chemical structures including the nitroimidazoles, phenothiazines, butyrophenones, halopyrimidines, benzamides and nicotinamides are known to possess radio- and chemosensitizing properties (Horsman, M. R. et al., Acta Oncologica 34:571, 1995; Brown, J. M. et al., Cancer Treatment Symposia 1, 85-101, 1984; Pu, A. T. et al., Oncology 9(8):707-21, 1995; George, K. C. and Singh, B. B., Indian J. Expt. Biol. 22:305-07, 1984; Kennedy, K. A. et al., Int. J. Radiat. Oncol. Biol. Phys. 12:1367-70, 1986; U.S. Pat. No. 5,340,565; Charp, P. A. and Regan, J. D., Biochim. Biophys. Acta 824:34-39, 1985, Ganapthi, R. et al., Biochem. Biophys. Res. Commun. 131:912-19, 1985; Lazo, J. S. et al., Cancer Res. 45:2103-09, 1985; Lazo, J. S. et al., Cancer Res. 46:2236-40, 1986). Common chemical structural features linking these diverse agents as radio- and chemosensitizers are not known in the prior art. U.S. Pat. Nos. 5,340,565, 5,215,738, 5,032,617 and 5,041,653 teach that benzamides and nicotinamides can radio- and chemosensitize by several mechanisms of action including by inhibiting DNA repair, by directly damaging DNA and by increasing tumor blood flow thus decreasing hypoxic resistance to tumor cell killing. The chemical features previously identified giving these classes of drugs radio- and chemosensitizing properties were di, mono- or un-N-substituted (xe2x80x94CONH2) or (xe2x80x94CSNH2) substitutions of the pyridine and benzene rings along with other aryl substitutions in structures I, II and III described below.
Structure I (from U.S. Pat. No. 5,340,565) has the formula 
wherein
X is any compatible aliphatic or aryl mono (xe2x80x94NHX) or di-substitutions (xe2x80x94NX2); and
Y can be from 0 to 5 substitutions of a compatible chemical structure, for example (but not limited to) a group consisting of: H, OR, SR or NHR in which R is H, hydrocarbyl (1-6 C) including cyclic and unsaturated hydrocarbyl, optionally substituted with 1 or 2 substituents selected from the group consisting of halo, hydroxy, epoxy, alkoxy, alkylthio, amino including morpholino, acyloxy and acylamido and their thio analogs, alkylsulfonyl or alkylphosphonyl, carboxy or alkoxycarbonyl, or carbamyl or alkylcarbamyl, and in which R can optionally be interrupted by a single ether (xe2x80x94Oxe2x80x94) linkage; or Y is O(CO)R, NH(CO)R, O(SO)R, or O(POR)R in which R is as above defined.
Structure II (from U.S. Pat. No. 5,215,738) has the formula 
wherein
X is O or S; and
Z is H, OR, SR or NHR in which R is H, hydrocarbyl (1-6 C) including cyclic and unsaturated hydrocarbyl, optionally substituted with 1 or 2 substituents selected from the group consisting of halo, hydroxy, epoxy, alkoxy, alkylthio, amino including morpholino, acyloxy and acylamido and their thio analogs, alkylsulfonyl or alkylphosphonyl, carboxy or alkoxycarbonyl, or carbamyl or alkylcarbamyl, and in which R can optionally be interrupted by a single ether (xe2x80x94Oxe2x80x94) linkage; or Z is O(CO) R, NH(CO)R, O(SO) R, or O(POR) R in which R is as above defined.
Structure III (from U.S. Pat. No. 5,041,653) has the formula 
wherein
x is O or S;
Y is H, Me, OMe, OEt acetoxy or acetamido; and
Z is OR or NHR in which R is H, straight chain alkyl (1-6 C) optionally substituted with 1 or 2 substituents selected from the group consisting of halo, hydroxy, epoxy, alkoxy, amino, acyloxy and acylamido, and in which R can optionally be interrupted by a single ether (xe2x80x94Oxe2x80x94) linkage; or O(CO)R or NH(CO)R in which R is as above defined.
In addition, prior art teaches that some analogs of the benzamides (Lybak, S. and Pero, R. W., Carcinogenesis 12:1613-17, 1991; Olsson, A. et al., Carcinogenesis 16:1029-35, 1995; George, A. M. et al., Int. J. Radiat. Biol. 49:783-98, 1986; Horsman et al., Int. J. Radiat. Oncol. Biol. Phys. 12:1307-10, 1986), nicotinamides (Horsman, M. R. et al., Radiat. Res. 118:139-50, 1989; Ben Hur, E. et al., Radiat. Res. 97:546, 1984; Horsman, M. R., Acta Oncologica 34:571, 1995), phenothiazines (Rosenthal, S. A. and Hart, W. N., Yale J. Biol. Med. 61:39-49, 1988), butyrophenones (U.S. Pat. No. 5,340,565) and halopyrimidines (Pu, A. T. et al., Oncology 9(8):707-21, 1995) can either directly by reacting with DNA, or directly by reacting with some chemical intermediate that in turn is converted to a DNA reactive intermediate, or indirectly by causing an increase in oxygen uptake by tumors which in turn can form DNA binding radicals, or indirectly by inhibiting DNA repair, cause DNA and other cell constituents to become damaged resulting in antitumor or radio- and chemosensitization. However, there is no prior knowledge in the literature that there are common chemical structural features which can give this diverse group of agents properties of antitumor or radio- and chemosensitization by a variety of mechanisms that amplify the levels of cellular DNA damage.
Among the specific compounds thus considered in the prior art are nicotinamide (hereinafter sometimes referred to as NAM), 4-amino-5-chloro-N-(2-diethylamino-ethyl)-2-methoxybenzamide (hereinafter sometimes referred to as metoclopramide or MCA), and their acid addition salts, e.g. metoclopramide hydrochloride (metoclopramide HCl).
The present invention, in a first aspect, broadly contemplates the provision of a method of inhibiting or killing tumor or cancer cells in a human patient, consisting essentially of treating the patient with a composition selected from the group consisting of aryl N-substituted carboxamides having one or more aryl halo or one or, more aromatic nitrogens, acid addition salts of these carboxamides, and mixtures thereof. In this method, the defined carboxamides act directly as chemotherapeutic agents, not merely as sensitizers for radiation and other chemotherapeutic agents. The term xe2x80x9cconsisting essentially,xe2x80x9d as used in the definition of the above-described method, excludes the use or presence of radiation or chemotherapeutic agents (other than the stated carboxamides and/or acid addition salts thereof) in the practice of the method.
The invention in a second aspect contemplates the provision of a method of inhibiting or killing tumor or cancer cells in a human patient, consisting essentially of treating the patient with radiation or a chemotherapeutic agent together with a composition selected from the group consisting of N-substituted nicotinamides, N-(2-diethylamino-ethyl)-4-amino-3-chlorobenzamide (hereinafter sometimes referred to as 3-chloro-procainamide or 3-CPA), their acid addition salts, and mixtures thereof, in an amount effective to enhance the cytotoxicity of the radiation or chemotherapeutic agent employed. The selected composition, in the latter method, acts as a sensitizer for the radiation or chemotherapeutic agent. The compositions used as such sensitizers, in accordance with the invention in this aspect, are novel in themselves or have at least not heretofore been recognized as capable of acting as sensitizers in radiation or chemotherapeutic treatments. They are within the broadly defined class of aryl N-substituted carboxamides having one or more aryl halo or one or more aromatic nitrogens.
In further important specific aspects, the invention contemplates the provision of certain novel compositions within the last-mentioned class and suitable for use in the practice of one or more of the above-stated methods of the invention; and the use of such compositions in the same methods. These compositions are the compounds N-(2-diethylamino-ethyl)nicotinamide (which is an N-substituted nicotinamide, and is hereinafter sometimes referred to as N-NAM), N-(2-diethylamino-ethyl)-4-amino-3-chlorobenzamide (i.e., 3-chloro-prcainamide, mentioned above), their acid addition salts, and mixtures thereof. Preferred acid addition salts are the hydrochlorides, viz., N-(2-diethylaminoethyl) nicotinamide HCl and 3-chloro-procainamide HCl.
Stated broadly, the invention in significant aspects is based on the identification of chemical features that impart properties of radio- and chemosensitization to some members of the group of agents discussed in the above-cited prior art, and embraces the discovery that agents having such properties include a new class of drugs called the N-substituted nicotinamides (e.g. N-NAM).
None of the prior art discussed above teaches the chemical features important to the present invention. For example, this invention embraces the discovery that the presence of an aryl constituent containing one or more halo substitutions (e.g. a halogenated benzamide), or an aromatic nitrogen (e.g. nicotinamide), or an equivalently appropriate reactive aromatic substitution (e.g. an aromatic sulfur (xe2x80x94Sxe2x80x94) or oxygen (xe2x80x94Oxe2x80x94)) needs to be combined with an N-substitution of the amide group of an existing carboxamide group (e.g. diethylaminoethyl side chain group) to give the resulting molecules the properties of inhibition of DNA repair, potentiation of DNA damage and a sensitized cytotoxicity.
These features may be represented by formula (A) 
wherein
W is O or S;
Q is MHX or MX2 where M is N, O or S and X is any compatible aliphatic or aryl substitution;
Y can be from 0 to 5 substitutions of a chemical structure, for example, but not limited to a group consisting of: H, OR, SR or NHR in which R is H, hydrocarbyl (1-6 C) including cyclic and unsaturated hydrocarbyl, optionally substituted with 1 or 2 substituents selected from the group consisting of halo, hydroxy, epoxy, alkoxy, alkylthio, amino including morpholino, acyloxy and acylamido and their thio analogs, alkylsulfonyl or alkylphosphonyl, carboxy or alkoxycarbonyl, or carbamyl or alkylcarbamyl, and in which R can optionally be interrupted by a single ether (xe2x80x94Oxe2x80x94) linkage; or Y is O(CO)R, NH(CO)R, O(SO)R, or O(POR)R in which R is as above defined; and
Z is one or more aromatic halo substitutions or one or more aromatic nitrogens or appropriately equivalent reactive aromatic substitutions such as a ring sulfur (i.e., xe2x80x94Sxe2x80x94) or oxygen (xe2x80x94Oxe2x80x94).
These structural requirements can be satisfied by benzamide and nicotinamide analogs as well as condensed aromatic ring systems such as suggested by but not limited to: quinolines, anthracenes, anthraquinones, quinones, phenothiazines, naphthalenes, and butyrophenones that contain a substitutable nitrogen (e.g. carboxamide) and at least one aromatic halo or aromatic nitrogen substitution.
Theoretically the discoveries embraced by the invention also teach that the N-substituted carboxamide structural requirement for antitumor or radio- and chemosensitizing properties could be replaced by an aryl carbonyl containing ester (aryl-COOxe2x80x94R, aryl-COSxe2x80x94R or aryl-COPxe2x80x94R) where R is equal to any substitutable aliphatic or aromatic group (e.g. a diethylaminoethyl side chain).
The invention in important respects, therefore, relates to the discovery of the chemical structural features that are important to give drugs antitumor or radio- and chemosensitizing properties, of potentiation of DNA damage resulting in tumor cytotoxicity. In its broadest sense, the essential common chemical features are an aryl N-substituted carboxamide and either at least one aromatic halo or aromatic nitrogen. The N-substituted benzamide analog, procainamide, will be shown here to be inactive because it did not contain an aromatic halo substitution along with the presence of an aryl N-substituted carboxamide (e.g. the diethylaminoethyl side chain present in metoclopramide or 3-chloro-procainamide). Moreover, metoclopramide and 3-chloroprocainamide but not procainamide could be shown to react with radiation which is a potential radiosensitizing event. These data are shown to be paralleled by in vitro cytotoxicity data that established metoclopramide and 3-chloro-procainamide, but again not procainamide, as having the properties to sensitize apoptotic cell killing by radiation. Together the data presented here indicate that both halo aromatic substitutions as well as N-substituted benzamides are necessary to give antitumor or radio- and chemosensitizing properties.
In another aspect this invention relates to the presence of an aromatic nitrogen substitution together with the presence of an aryl carboxamide to give antitumor or radio- and chemosensitizing properties. Such drugs are represented by the N-substituted nicotinamides or pyrazinamides for which N-(2-diethylamino-ethyl)nicotinamide is an example. In addition, it is now found that although N-(2-diethylamino-ethyl)nicotinamide, and to a much lesser degree nicotinamide, possess the potential radio-sensitizing property of reacting with radiation as a mechanism of initiating oxidative stress and increasing the potential for DNA damage induction, it is only N-(2-diethylamino-ethyl) nicotinamide and not nicotinamide, that can enhance apoptotic cell killing by radiation. It is hypothesized that an N-substitution of the carboxamide group of nicotinamide blocks the metabolic conversion of the nicotinamide moiety to NAD, and thus allows the chemical reactivity of the aromatic nitrogen with radiation to produce stress-induced cellular damage, and consequently, potentiates apoptotic cell killing by radiation plus the drug. It is clear then that N-substitutions of the carboxamide of nicotinamide permit the aromatic nitrogen to react with radiation or other radical generating systems to initiate an oxidative stressing cascade, instead of allowing the normal aromatic nitrogen cellular reaction of nicotinamide with the ribose moiety of adenine dinucleotide to form the energy source, NAD. These properties of N-substituted nicotinamides are novel and have never been heretofore described. They constitute a new class of agents with a high potential to possess antitumor or radio- and chemosensitizing properties.
Moreover, it should be noted that because both N-substituted benzamides (as shown in U.S. Pat. No. 5,340,565) and N-substituted nicotinamides (as now discovered, as an aspect of the present invention) possess antitumor or radio- and chemosensitizing properties, there is a great likelihood that other aromatic condensed ring systems can be identified that contain similar prerequisite structural moieties including, but not limited to a N-substituted aryl carboxamide giving such agents antitumor or radio- and chemosensitizing properties.
Additionally it may be noted that certain components of formula (III) above, wherein Z is in the 3-position, and wherein Z is OR or NHR in which R is substituted or interrupted with xe2x80x94Oxe2x80x94, or Z is O(CO)R or NH(CO)R in which R is substituted or interrupted with xe2x80x94Oxe2x80x94, are novel.